The human body communication uses a human body as a channel. Data is transmitted using a transmitter connected to a part of the human body. The transmitted data is recovered using a receiver connected to another part of the human body or outside the human body. The human body communication allows communication between portable devices or communication between a fixed device and a user to be made through user's contact. For example, communication between a personal digital assistant (PDA), a portable computer, a digital camera, an MP3 player and a mobile phone can be performed through user's contact. Such communication through user's contact may also be applied to, e.g., printers, credit cards, television reception, entrance systems and payment systems for transportation.
The human body transmits radio waves anisotropically while the air transmits radio waves isotropically. Thus, it is difficult for a receiver existing at an arbitrary position of the human body to receive accurate radio waves from a transmitter. The electric waves traveling through the human body loses more energy than those traveling through the air. The human body easily receives an interference signal from surroundings because of its conductivity.